Reputation
Next tag badge:
106/100 score
19/20 answers
Badges
2 32 103
Impact
~356k people reached

Apr
17
comment Key space vs Cardinality of 1024-bit RSA
To avoid duplicate moduli we want $p<q$, that about halves the cardinality. And then, what about $e$ ? Setting a fixed $e=3$ reduces the cardinality by a factor of about $4/9$. If $e$ is allowed to vary, and we defined an RSA key as $(p\cdot q,e)$, our cardinality increases (and we should account for equivalent $e$ if very large $e$ are allowed). And then, many practical RSA key generation algorithms only generate primes of a certain form (like, such that $p-1$ and $p+1$ each have a known prime factor of a fixed bit size) and that reduces the cardinality of what they could generate.
Apr
16
revised Is there a way to use bcrypt with passwords longer than 72 bytes securely?
polish
Apr
16
revised Is there a way to use bcrypt with passwords longer than 72 bytes securely?
Formalize the hash requirements
Apr
15
answered Is there a way to use bcrypt with passwords longer than 72 bytes securely?
Apr
15
revised Factoring two RSA moduli $N_i=p_i\cdot q_i$ knowing that $p_2=p_1+2$?
fix a notation
Apr
15
asked Factoring two RSA moduli $N_i=p_i\cdot q_i$ knowing that $p_2=p_1+2$?
Apr
15
comment Difference between IPSEC SA and CHILD SA
This is off-topic, because that's very specific to a particular security product, rather than cryptosystem. I suggest migration to security.stackexchange.com
Apr
15
comment Asymmetric encryption that is secure for (almost) any foreseeable future
It is not stated to what certainty degree it is required that the scheme remains secure after 1000 years, and that's an important parameter. It is much easier to predict very long term things with 30% chances to be wrong, rather than with 0.03% chances (a residual risk level often accepted in security, about that of having one's Smart Card pin guessed). One reason many key length estimates in the distant future are so conservative is that they are made with the intend to only err on the safe side.
Apr
15
comment Factoring two RSA modulus with known $|p_1 - p_2| < \ell $
I fail to see how the examination of the bits of the ratio$N_1\over N_2$ reveals information on $a$ (as stated in the but-last paragraph of the current answer). As a minor aside, $|p_1-p_2|\le2^s$ is not quite a sufficient condition to insure that $\lfloor p_1/2^s\rfloor=\lfloor p_2/2^s\rfloor$, thus existence of $a$. That part is easily fixable: with $s=\lceil\log_2\ell\rceil+4$, it is quite likely $a$ exists.
Apr
15
comment Factoring two RSA modulus with known $|p_1 - p_2| < \ell $
@mikeazo: in the present question $0<|p_1-p_2|<\ell$, in the other question that you linked (transposing the notation to match that in the present question), we have $|p_1-q_1|<\ell$. $\;$ I have not understood the proposed attack, and fail to see one. $\;$ I second Lisbeth's approach to first try to solve the problem with $p_1-p_2=2$.
Apr
14
revised The effect of truncated hash on entropy
fix my totally bogus usage of small-o notation
Apr
14
comment Meaning of Signature hash algorithm field in certificate
@Dandan: only $Pub_B$ is in the certificate that we are talking about in the question and answer. $Pub_A$ is the public key of the certification authority, is typically designated (not contained) in the certificate's data, and is known and trusted either because it is built in the software that verifies certificates, or because it is introduced by another certificate including a signature verified by yet another known and trusted public key. Sometime $Pub_A=Pub_B$, this is a self-signed certificate, and we can trust these only if they are known to come from a trusted source.
Apr
14
comment RFID Protocol Cryptanalysis
Think about it again: with the protocol as described, some message loss can turn the step "they both add $r_1$ to the key set" into something where one of TAG or READER did this, and the other did not.
Apr
14
comment RFID Protocol Cryptanalysis
In RFID, the TAG goes from a READER to another; as far as I understand the scheme outlined, the various readers need to know the current sate of a given TAG, by communicating between each others in some way, which is not something to lightly consider for granted in the physical world. $\;$ Independently, it is frequent that a message is lost between TAG and READER (in either direction), and the protocol outlined does not seem to account for that inescapable fact. $\;$ So before asking if it's secure (and defining the meaning of that): does it even work in the absence of adversary?
Apr
14
comment Benefit of using random key in Shamir's Secret Sharing
I would be very surprised that the shares in the first example decode to "Hello" using any natural (nothing-up-my-sleeves) implementation of Shamir secret sharing. $\;$ Perhaps you are confusing key (usually understood as the secret value of a share, or shares, or the secret shared), and index (the identifier of a share, usually public), and really wanting to ask if there is benefit in using random index in Shamir secret sharing? In any case, it would help if you defined what benefit you expect; can't be about secrecy of the shared secret, Shamir secret sharing provably insures this.
Apr
14
revised Meaning of Signature hash algorithm field in certificate
Give another use of signatureAlgorithm
Apr
14
revised Meaning of Signature hash algorithm field in certificate
Polish
Apr
14
answered Meaning of Signature hash algorithm field in certificate
Apr
13
revised How does the Blowfish algorithm key initialization work
State the keysize limits in uniform units. Enough.
Apr
13
revised How does the Blowfish algorithm key initialization work
Ah and we have those pesky variants on the upper size of the key, too.